A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance...A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for Al6061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.展开更多
Effects of rare earth element La on the microstructure of Cumatrix diamond tools were researched under the conditions of variousmaterials components and the process parameters in order to improvematerials properties. ...Effects of rare earth element La on the microstructure of Cumatrix diamond tools were researched under the conditions of variousmaterials components and the process parameters in order to improvematerials properties. SEM, XPS and X-ray were used to investigate thefracture section, microstructure and the element valence inmaterials. The Results shown that the combination of rare earthelement La and transition element Ti is advantageous to the bondingstate Between diamond particles and matrix, so it can improve thematerials properties. Suitable sintering temperature is 790 deg. C.展开更多
Al-Si metal matrix composites (MMCs) reinforced with 20 vol.% alumina-silicate shot fibers (Al2O3-SiO2(sf)) were fabricated by an infiltration squeeze method. Pure Pr metal was added into these composites. The effect ...Al-Si metal matrix composites (MMCs) reinforced with 20 vol.% alumina-silicate shot fibers (Al2O3-SiO2(sf)) were fabricated by an infiltration squeeze method. Pure Pr metal was added into these composites. The effect of Pr addition on the microstructure evolution of Al-Si MMCs was investigated by SEM,TEM,and EDS. Pr addition is favorable to make uniform microstructures with the modified eutectic Si crystal. PrAlSi phase with high contents of Pr and Si is observed on the interface between the fiber and the m...展开更多
The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning elect...The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [展开更多
A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide (Eu_2O_3) was developed. The spectral interference,matrix effect,instru...A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide (Eu_2O_3) was developed. The spectral interference,matrix effect,instrument parameters fluctuation were investigated and the optimized experimental conditions were established. Under the selected conditions,the detection limits of the method are 3～7 ng·L (-1),the RSD is varied between 2.1%～8.4%,and the percentage recovery is ranged from 90% to 113% for the analytes. The solid detection limit for gross amount of 13 rare earth impurities is 0.19 μg·g (-1) when the matrix (Eu) concentration of 0.1 mg·ml (-1) was chosen. Compared with the reported methods in the literature,this method has several attractive features: simple,small sample amount required,no internal standard and matrix matching requirements.展开更多
The Al2O3-SiO2(sf)(volume fraction,20%)/Al-12.6Si metal matrix composites(MMCs)with or without rare earth Pr addition were fabricated by infiltration squeeze method.Effect of Pr addition on microstructures and fractog...The Al2O3-SiO2(sf)(volume fraction,20%)/Al-12.6Si metal matrix composites(MMCs)with or without rare earth Pr addition were fabricated by infiltration squeeze method.Effect of Pr addition on microstructures and fractographs of Al-Si MMCs was investigated by SEM and TEM.Tensile properties at room temperature and 200℃were tested.It is shown that the addition of Pr is favorable to produce uniform microstructures and modify the eutectic Si crystal effectively.Compounds/intermetallics with high content of Pr are formed at the interface between short fiber and matrix.Yield strength(σ 0.2 ),ultimate tensile strength(σ b)and fracture elongation of Al-Si MMCs are improved by adding suitable amount of Pr.Compared with those values of Al-Si based MMC at 200 ℃,σ 0.2 andσ bof MMC with 0.29%Pr are increased by 33%and 55%,respectively.The tensile fracture surface of Al-Si MMCs with Pr addition presents ductile fracture features.展开更多
Based on the combination of Racah＇s group-theoretical consideration with Slater＇s wavefunction, a 91 ×91 complete energy matrix is established in tetragonal ligand field D2d for Pr3＋ ion. Thus, the Stark energ...Based on the combination of Racah＇s group-theoretical consideration with Slater＇s wavefunction, a 91 ×91 complete energy matrix is established in tetragonal ligand field D2d for Pr3＋ ion. Thus, the Stark energy-levels of Pr3＋ ions doped separately in LiYF4 and LiBiF4 crystals are calculated, and our calculations imply that the complete energy matrix method can be used as an effective tool to calculate the energy-levels of the systems doped by rare earth ions. Besides, the influence of Pr3＋ on energy-level splitting is investigated, and the similarities and the differences between the two doped crystals are demonstrated in detail by comparing their several pairs of curves and crystal field strength quantities. We see that the energy splitting patterns are similar and the crystal field interaction of LiYF4：Pr3＋ is stronger than that of LiBiF4：Pr3＋.展开更多
The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile propertie...The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile properties of the composites were analysed and studied. The results showed that the coated AI2O3 particles are able to disperse homogeneously in the aluminum liquid. The microstructure of the composites is more even in comparison with that of as-received powders. The tensile testing indicated that mechanical properties of the coated-AI2O3p/6061AI composites are better than those of uncoated particles. In the composite with 30% volume fraction, the tensile strength, yield strength as well as elongation is increased by 29.8%, 38.4% and 10.3%, respectively. The SEM analysis of fracture indicated that the dimples of the coated-Al2O3p/6061Al composites are more even.展开更多
Quantitative dynamics and viability of a rare and wild Cycas fairylakea population were studied with a time-specific life table, a Leslie matrix model and a survival function in order to provide scientific guidance fo...Quantitative dynamics and viability of a rare and wild Cycas fairylakea population were studied with a time-specific life table, a Leslie matrix model and a survival function in order to provide scientific guidance for its protection. The results of the time- specific life table show that this C. fairylakea population suffered a high death rate in three age classes, i.e., age class 1 （0-15 years）, V （61-75 years） and VI （76-90 years）. The Leslie matrix model suggests that the number of plants would decline from the present 1613 to 59 per hectare in 150 years. Furthermore, the viability analysis indicates that seedlings have the highest mortality density rate and that middle-aged plants （i.e., 61-75 years, 76-90 years） have high mortality density rate and hazard rate. These conditions affect natural regeneration of the population and lead to a lack of seedlings which in turn causes the extinction of the population. An in situ conservation of the population should be established and protection measures taken as soon as possible.展开更多
Polymer matrix RE-Fe giant magnetostrictire composite （GMPC） was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experi...Polymer matrix RE-Fe giant magnetostrictire composite （GMPC） was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.展开更多
Binary and ternary terbium complexes were synthesized: Tb(N PA) 3·4H 2O and Tb(N PA) 3(phen·2H 2O (N HPA = N phenyl 2 aminobenzoic acid and phen = 1,10 phenanthroline). These complexes were introd...Binary and ternary terbium complexes were synthesized: Tb(N PA) 3·4H 2O and Tb(N PA) 3(phen·2H 2O (N HPA = N phenyl 2 aminobenzoic acid and phen = 1,10 phenanthroline). These complexes were introduced into inorganic polymeric porous silica matrix by the sol gel method. The luminescence behavior of the complexes in silica gels was compared with the corresponding solid state complexes by means of emission, excitation spectra and luminescence lifetimes. The result indicates that the terbium ions show fewer emission lines and lower emission intensities in the silica gel than those in pure terbium complexes. The lifetimes of terbium ions in silica gel doped with terbium complexes become longer than those of terbium complexes.展开更多
文摘A new method for corrosion protection of Al-based metal matrix composites (MMC) was developed using two-step process, which involves anodizing in H2SO4 solution and sealing in rare earth solution. Corrosion resistance of the treated surface was evaluated with polarization curves. The results showed that the effect of the protection using rare earth sealing is equivalent to that using chromate sealing for Al6061/SiCp. The rare earth metal salt can be an alternative to the toxic chromate for sealing anodized Al MMC.
文摘Effects of rare earth element La on the microstructure of Cumatrix diamond tools were researched under the conditions of variousmaterials components and the process parameters in order to improvematerials properties. SEM, XPS and X-ray were used to investigate thefracture section, microstructure and the element valence inmaterials. The Results shown that the combination of rare earthelement La and transition element Ti is advantageous to the bondingstate Between diamond particles and matrix, so it can improve thematerials properties. Suitable sintering temperature is 790 deg. C.
文摘Al-Si metal matrix composites (MMCs) reinforced with 20 vol.% alumina-silicate shot fibers (Al2O3-SiO2(sf)) were fabricated by an infiltration squeeze method. Pure Pr metal was added into these composites. The effect of Pr addition on the microstructure evolution of Al-Si MMCs was investigated by SEM,TEM,and EDS. Pr addition is favorable to make uniform microstructures with the modified eutectic Si crystal. PrAlSi phase with high contents of Pr and Si is observed on the interface between the fiber and the m...
文摘The processes of mixed rare earth metal (REM) conversion coatings on 2024 alloy and Al6061/SiC p metal matrix composites (MMC) were introduced. The coatings were examined to be honeycomb like feature by scanning electron microscope. X ray diffraction analysis revealed that the coatings are amorphous structure. The results of X ray photoelectron spectroscopy indicated that the mixed REM conversion coatings consist predominantly of Ce and O, the contents of other rare earth elements (such as La, Pr) are relatively low, the coatings are about 2～4 μm thickness with excellent adhesion and wearability. The results of mass loss test showed that the mixed REM conversion coatings produce corrosion resistant surface of 2024 alloy and Al6061/SiC p. [
文摘A novel inductively coupled plasma mass spectrometry method for direct determination of trace rare earth impurities in high purity europium oxide (Eu_2O_3) was developed. The spectral interference,matrix effect,instrument parameters fluctuation were investigated and the optimized experimental conditions were established. Under the selected conditions,the detection limits of the method are 3～7 ng·L (-1),the RSD is varied between 2.1%～8.4%,and the percentage recovery is ranged from 90% to 113% for the analytes. The solid detection limit for gross amount of 13 rare earth impurities is 0.19 μg·g (-1) when the matrix (Eu) concentration of 0.1 mg·ml (-1) was chosen. Compared with the reported methods in the literature,this method has several attractive features: simple,small sample amount required,no internal standard and matrix matching requirements.
基金Project(2008B080703001)supported by Guangdong Provincial Science&Technology Breau,China
文摘The Al2O3-SiO2(sf)(volume fraction,20%)/Al-12.6Si metal matrix composites(MMCs)with or without rare earth Pr addition were fabricated by infiltration squeeze method.Effect of Pr addition on microstructures and fractographs of Al-Si MMCs was investigated by SEM and TEM.Tensile properties at room temperature and 200℃were tested.It is shown that the addition of Pr is favorable to produce uniform microstructures and modify the eutectic Si crystal effectively.Compounds/intermetallics with high content of Pr are formed at the interface between short fiber and matrix.Yield strength(σ 0.2 ),ultimate tensile strength(σ b)and fracture elongation of Al-Si MMCs are improved by adding suitable amount of Pr.Compared with those values of Al-Si based MMC at 200 ℃,σ 0.2 andσ bof MMC with 0.29%Pr are increased by 33%and 55%,respectively.The tensile fracture surface of Al-Si MMCs with Pr addition presents ductile fracture features.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10774103 and 10974138)
文摘Based on the combination of Racah＇s group-theoretical consideration with Slater＇s wavefunction, a 91 ×91 complete energy matrix is established in tetragonal ligand field D2d for Pr3＋ ion. Thus, the Stark energy-levels of Pr3＋ ions doped separately in LiYF4 and LiBiF4 crystals are calculated, and our calculations imply that the complete energy matrix method can be used as an effective tool to calculate the energy-levels of the systems doped by rare earth ions. Besides, the influence of Pr3＋ on energy-level splitting is investigated, and the similarities and the differences between the two doped crystals are demonstrated in detail by comparing their several pairs of curves and crystal field strength quantities. We see that the energy splitting patterns are similar and the crystal field interaction of LiYF4：Pr3＋ is stronger than that of LiBiF4：Pr3＋.
基金This investigation was supported by the National Natural Science Foundation of China(No.59771014 and 50071019).The supports are gratefully acknowledged.
文摘The liquid-phase coating method was used to deposit Y2O3 ceramic on the surface of α-Al2O3. The coated-Al2O3p/6061AI composites were produced using squeeze casting technology. The microstructure and tensile properties of the composites were analysed and studied. The results showed that the coated AI2O3 particles are able to disperse homogeneously in the aluminum liquid. The microstructure of the composites is more even in comparison with that of as-received powders. The tensile testing indicated that mechanical properties of the coated-AI2O3p/6061AI composites are better than those of uncoated particles. In the composite with 30% volume fraction, the tensile strength, yield strength as well as elongation is increased by 29.8%, 38.4% and 10.3%, respectively. The SEM analysis of fracture indicated that the dimples of the coated-Al2O3p/6061Al composites are more even.
文摘Quantitative dynamics and viability of a rare and wild Cycas fairylakea population were studied with a time-specific life table, a Leslie matrix model and a survival function in order to provide scientific guidance for its protection. The results of the time- specific life table show that this C. fairylakea population suffered a high death rate in three age classes, i.e., age class 1 （0-15 years）, V （61-75 years） and VI （76-90 years）. The Leslie matrix model suggests that the number of plants would decline from the present 1613 to 59 per hectare in 150 years. Furthermore, the viability analysis indicates that seedlings have the highest mortality density rate and that middle-aged plants （i.e., 61-75 years, 76-90 years） have high mortality density rate and hazard rate. These conditions affect natural regeneration of the population and lead to a lack of seedlings which in turn causes the extinction of the population. An in situ conservation of the population should be established and protection measures taken as soon as possible.
文摘Polymer matrix RE-Fe giant magnetostrictire composite （GMPC） was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.
文摘Binary and ternary terbium complexes were synthesized: Tb(N PA) 3·4H 2O and Tb(N PA) 3(phen·2H 2O (N HPA = N phenyl 2 aminobenzoic acid and phen = 1,10 phenanthroline). These complexes were introduced into inorganic polymeric porous silica matrix by the sol gel method. The luminescence behavior of the complexes in silica gels was compared with the corresponding solid state complexes by means of emission, excitation spectra and luminescence lifetimes. The result indicates that the terbium ions show fewer emission lines and lower emission intensities in the silica gel than those in pure terbium complexes. The lifetimes of terbium ions in silica gel doped with terbium complexes become longer than those of terbium complexes.
